Field of Invention
The present invention relates to a technical field of the drilling equipment, and more particularly is adapted for the gas drilling technology to drill directional wells, horizontal wells and highly deviated wells.
Description of Related Arts
Gas drilling is an underbalanced drilling mode which utilizes the gas (including air, nitrogen, natural gas and diesel exhaust) as the circulating medium, injects the high-pressure gas into the wells through the drill string by the ground gas compressor, depends on the energy of annular high-speed gas for bringing drill cuttings from the bottom hole back to the ground and detaching the solid/gas on the ground, and the detached combustible gas is released, dust-removed and noise-reduced. Currently, the gas drilling technology is universally well-known as a practical technology, which is capable of effectively shortening the drilling time, liberating the hydrocarbon zone and reducing the drilling cost. It has become an important means for efficiently developing the oil and gas fields. However, the conventional gas drilling technologies and equipments are mainly adapted for vertical wells, and unable to highly-effectively complete the directional drilling for forming directional wells, horizontal wells and highly deviated wells, which seriously limits the application ranges of the gas drilling. The main reason of the above shortcomings of the gas drilling is lack of the key downhole equipment, which is reliable and suitable for the directional drill of the gas drilling, namely, the gas drilling screw drill. The conventional gas drilling screw drills have basically same principles and structures with the liquid (mud drilling liquid) screw drills, and only the circulating medium is transformed from the incompressible liquid into compressible gas. Because the gas is the compressible medium, during application, the conventional gas screw drill outputs low torque, and unstable rotation speed and torque, which causes that the drill is stopped, and then rotates at high speed after being released, namely, the “overspeed” phenomenon, so that the conventional gas drilling screw drill has bad performance and low service life, is unable to stably, reliably and highly effectively drill directional wells.
The key to success of directional wells, horizontal wells and highly deviated wells by the gas drilling is to overcome the “overspeed” phenomenon of the gas screw for achieving the stable output of the gas drilling torque, and prolonging the service life of the drill. Therefore, the present invention designs a gas screw drill which is adapted for the directional wells, horizontal wells and highly deviated wells of the gas drilling, utilizes the gas-drive hydraulic-motion self-circulation, is able to achieve the ground remotely-controlled speed control and stably output the torque. The present invention is based on material mechanics, engineering mechanics and fluid dynamics, through reasonable designs, depends on the “engine” principles, sufficiently utilizes the high-pressure, high-flow and compressible circulating gas of the gas drilling to design the downhole “engine”. It utilizes the high-pressure gas outputted by the ground compressor to drive the downhole screw piston mechanism to move up and down at high speed, so as to drive the uncompressible liquid in the screw to achieve the self-circulating motion, for allowing the liquid to drive the rotor to rotate, so that the energy directional transformation of the gas pressure energy-mechanical energy (piston)-hydraulic pressure energy-mechanical energy (rotor) is realized. Furthermore, the speed of the piston is remotely controlled by the ground, so that the rotation speed of the screw is not affected by the changing gas flow rate, for outputting the stable and large enough torque to the drilling bit, thereby achieving the directional drilling operation of the gas drilling.